Websites that detect ad-blockers to stop their users from reading webpages could be illegal under European law.

Alexander Hanff, a privacy campaigner and programmer, says he has received a letter from the European Commission confirming that browser-side web scripts that pick out advert blockers access people’s personal data (ie: the plugin stored on their computer). Thus, just like you need to give permission to EU websites to access and store your cookies, ad-blocker detectors must ask for permission before probing your browser.